What acoustic treatments for vocal booth?

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knightfly

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Joined
Jan 18, 2002
“when you say "lumber",do you mean a piece of wood like a "rafter"?”

Yes. In John’s country, apparently the word is “timber” - normally, a
general term for building materials which means “ solid wood, direct from trees, cut to
a specific cross-section such as 2”x4”, called “dimensional lumber” here in the US.

“do 2x4's lumbers mean lumbers with 4" width,2" thick and...length...?"

I know this gets confusing, but read my last post again - the one where I explained
how/why
a 2x4 really is NOT 2” x 4” … and, yes the length of lumber
(boards,
or timbers) must be specified when you buy them - normally, such boards come in
even
lengths of feet in the US - such as 8 foot, 10 foot, etc… You usually figure
out what you need, ]
and sometimes buy lumber that is twice as long as what you need if the price is
better -
you then just cut two pieces from the one long one…

“Means that we've got 2 lumbers placed horizontally at the bottom and
the top,
and as much as needed vertical plates(=lumbers) going BETWEEN these 2 lumbers?(LENGTH=7,19'-2x2"?)”

Sort of - I’m not sure where you got the “-2x2” part.
Also, at least in the US, the carpenter’s terms are: a PLATE is the
horizontal framing member of a wall which is in contact with the floor on
which the wall is built. The STUDS are vertical framing members, such as
the 7.19’ pieces (in the case of your vocal booth) that go from
the plate on the floor up to the horizontal member on the ceiling; these
ceiling horizontals are normally called CAPS (like the cap you put on your head)

“Then means that the open angle due to the slope between wall
and plate should be caulked as much as possible,putting the "glue" before
the plate to improve the result(That outside angle at the max cavity depth
means that you put the 12" cavity on the left side of the wall,right?)"

Correct.

“the first time we had put the insulation board was just to check the
studs position?"

Yes.

“we do put them,BETWEEN the stud and not ON them?"

This is what I would do - if you mount the insulation board on TOP of the frame,
then mount the slats over the insulation board with screws, it would be nearly
impossible to maintain the critical slot width since the insulation board can flex
and compress. That would change the angle and position of the slats, relative
to each other. Since this is where the slot dimension is formed, merely
tightening some screws more than others would pull the slats one way or the
other, changing the slot width.

By mounting the slats DIRECTLY on the frame and placing the insulation board
BEHIND them, you have a hard surface joint between frame and slat, and can
set them very precisely, for example by using the spacer method I mentioned
at the first of this thread.


“if i"build a frame with 2x4's, positioning the side of the frame that is
toward the open area of the booth at 6" and 12" from the wall that will be
inside the trap",and if insulation board is put BETWEEN,then the cavity would be
shorten as much?"

Effectively, no. The outer surface of the slats determines the surface to be
used for modal calculations. The depth of the trap is not nearly as critical as
slot width/depth. As long as the insulation board is close to the slats, it will
serve its purpose of broadening the response of the trap and increasing the
amount of absorption. The air that is attempting to pass thru the insulation
still has to get past the slots, which, along with the slat width and depth
behind the slats, combine to determine frequency response.

“i'm still confuse with that:"placing them back from the outer
edge by at least 1/4", preferably 1/2" - one way would be to cut some
1" cleats and place them flush with the INSIDE edge of the studs, floor
to ceiling - run a bead of construction adhesive all the way around the
cleat, then press the insulation boards up against the cleat."Euh..”

A cleat is just a smaller board, normally fastened to a larger one to act as
a “stop” for some OTHER piece that needs to be accurately
located, with a surface you can glue or fasten to. Normally used in furniture
making, to support shelves, seats, etc. - In your case, these would be strips
of wood approximately ¾” to 1” square in cross section,
fastened to both sides of each stud lengthwise at the innermost edge, so
that you have a surface that will act as a “stop” and also
a glue surface for the mounting of the insulation board.

“I'm calculating for the center of each group of nodes, so f/o
will be 89, 187, and 266 using the longer dimension(5.7ft), or 95, 187,
281 hZ using the shorter dimension (5.2 ft)"
I'm not sure but...i always find 177hz instead of 187hz(longer dimension).
Am i wrong?"


177 is the second harmonic of the 6.35 foot dimension, which doesn &
#8217;t get changed. 187, however, is the AVERAGE between the lowest
and highest frequencies for second harmonics, when using the 5.2 foot
dimension caused by the deeper side of the trap. I picked that freq just
to be centered between the two extremes of the second harmonic so t
hat all 3 modes are covered. Given the variable depth of the trap, it won
’t make any difference to change things by 10 hZ. No, you&#8217
;re not figuring it wrong, just different.

Greg, if you haven't already been there, you REALLY need to look at John's
drawing of a trap. It explains almost exactly what I've been trying to explain,
other than the cleats. Click on this link -

http://www.saecollege.de/reference_material/index.html

Then, click on Absorbers, then click on the tab marked Mid Frequencies,
and look at the drawing. The only difference in what I'm recommending is the
variation in slat width and slot width, the values of which I posted just prior to
this.

From your questions, I'm not sure if you are just struggling with the translation
(again, much better than I ever could) or if you're not very familiar with building
techniques - if inexperience is the case, you would be wise to buy a book on basic
carpentry, including tools, skills, and methods.

This book,

http://www.amazon.com/dp/0865735778/?tag=r06fa-20

has the basics of carpentry, and would be a good beginner book if you haven't
yet learned about it...

just some food for thought; have you discovered what lumber sizes are available
in your area yet? Should be interesting comparing the two... Steve
 

audiowkstation

Well-Known Member
Joined
Jun 29, 2001
.......actually my bathroom works quite nice...depending on how I hang the towels.

Sorry folks....you guys are going into some great depth here..I love it!
 

knightfly

Well-Known Member
Joined
Jan 18, 2002
Hey Bill, glad to see ya here - funny you should mention that, I was just considering whether to "throw in the towel", as it were... :=) Steve

BTW, does anybody know what terms are used for the various parts of a building in France? Just a little unsure of how to 'splain some of this in a language I can barely recognize, let alone speak... Steve
 

audiowkstation

Well-Known Member
Joined
Jun 29, 2001
I like bathrooms for vocals because the outboard reverb deteriorates the quality too much..
Hang those towels where you need them.

(I got cha)
 

knightfly

Well-Known Member
Joined
Jan 18, 2002
Sooo, Bill, would you recommend those bathroom vocals be recorded wet, or dry? :=)
 

knightfly

Well-Known Member
Joined
Jan 18, 2002
That'd work - I'd expect some really squeaky clean recordings using that approach...
 

gregmusic

Guest
Ok Steve,I've just found time to resume all your explanations from your last post and before...

Now i'm getting things than i hadn't got yet(yeah, think i'm in the next step);BUT, here's my own "translation", it may reveal if i'm ok or not ,being in the same time a new summary!

-FIRST STEP: THE FRAME
- Two 2"x4"(originally) studs,horizontally mounted,one at the bottom,the other at the ceiling,both with angles cut at the connection with the 2 walls(2 connections:at 6"/at 12" from the original wall) and with caulk to prevent air from passing trough;
-Four 2"x4" studs(1 at the left wall,1 at the opposite wall,and the 2 last ones between),all vertically mounted BETWEEN the horizontal studs described above,square with them at their connections and caulked as usual;the 2 middle ones being mounted with insulation board as a guide for optimal positions.
===SO,these four studs should not be 5,19 long,BUT 5,19 less 2 times the horizontal studs width(since they are placed BETWEEN them),say 5,19-2x2" !...?

-SECOND STEP: THE INSULATION BOARDS
-Since the insulation boards should be placed BETWEEN the vertical studs,in order to fix them,we need to add 1"x1"cleats vertically mounted BEHIND the vertical studs showing a 1/2" width part of these cleats at the inner(left/right) side of the studs.So the insulation boards will be "stopped" there,fixed with glue and nails...Now we've got sort of "frames within the frame",putting THEORICALLY the outside edge of the insulation boards at 12" to 6" far from the original wall.
====I say THEORICALLY because if the (vertical) studs are in fact less than 2" deep,i mean 1,5",HOW can the insulation boards not go beyond the studs line?

THIRD STEP:THE SLATS/SLOTS
-Now we should fix the slats DIRECTLY ON the studs for better maintained position than it would be if just mounted on the insulation boards;The slats/slots width/depth depending on the matching cavity depth behind the insulation boards,boards which should be CLOSE to the slats for better absorption...
====BUT:The side of the frame that is toward the open area of the booth,WAS the "line"(going from 6" to 12" far from the original wall) used for modal calculations.So if you consider that " the outer surface of the SLATS determines the surface to be used for modal calculations",we'll have LESS depth than the average 9",but 9" + 1,5"(slats width) !....?

Again,sorry to repeat myself about the results from the room modes calculated for 5,2' and 5,7',i was speaking about the center of group of nodes FOR the 5,7' dimension,NOT for the 5,2 dimension.
=====For 5,2' dimensions H2,L2,W2=157,178,217/CENTER=187HZ====OK
=====For 5,7' dimensions H2,L2,W2=157,178,198/CENTER=177,5HZ but not 187HZ ??

Steve,i hope i'm not so far from the final thing !

Thanks again,

Greg
 

gregmusic

Guest
Sorry ,correction to my post:
"we'll have LESS depth than the average 9",but 9" + 1,5"(slats width) !....?">>>>>Correction:"We'll have MORE depth"( and less dimension in the room)
 

knightfly

Well-Known Member
Joined
Jan 18, 2002
Greg, I think we're almost there - your questions, sort of in order:

"SO,these four studs should not be 5,19 long,BUT 5,19 less 2 times the horizontal studs width(since they are placed BETWEEN them),say 5,19-2x2" !...?"

Yes, except they would be 7.19 feet minus the thickness of the two bottom and top horizontals, not 5.19 feet.

"I say THEORICALLY because if the (vertical) studs are in fact less than 2" deep,i mean 1,5",HOW can the insulation boards not go beyond the studs line?"

I think you have just one slight misunderstanding, my fault for not explaining more clearly - the vertical studs, which are 1.5" x 3.5", get placed between the two horizontals, with the LONGER (3.5") dimension turned so that from the front of the trap, you would see the NARROW edge of the stud. This way, there is a 3.5" depth, with plenty of room to place the cleat at the back edge and still have room for the insulation board in front of the cleats. When the frame is complete except for the slats and insulation board, all the pieces of the frame will have the same depth front-to-back, or in this case 3.5 inches.

"we'll have LESS depth than the average 9",but 9" + 1,5"(slats width) !....?">>>>>Correction:"We'll have MORE depth"( and less dimension in the room) "

Correct, but this is insignificant when viewed as a ratio of the overall dimension of the room versus 1.5" - that amount of change for the 5.2 foot dimension results in a frequency shift of less than 2 hZ, and ONLY for the width harmonics. The trap is tuned broader than that by means of the variable depth, so you would never hear the difference. Rupert Neve, in his wildest wet dreams, wouldn't hear it, for that matter. In fact, you could round the depth of the trap from 12"/6" (305mm/153mm) to 300mm/150mm if your measuring tools are graduated in mm, and the numbers don't change at all in the spreadsheet. That particular dimension isn't NEARLY as critical as the slot width. (Distance BETWEEN the slats)

"=====For 5,2' dimensions H2,L2,W2=157,178,217/CENTER=187HZ====OK
=====For 5,7' dimensions H2,L2,W2=157,178,198/CENTER=177,5HZ but not 187HZ ??"

Correct. for the 5.7' dimension, the AVERAGE and the L2 mode come within 0.25 hZ of each other. The shorter, 5.2' dimension at 217 hZ for W2, raises the AVERAGE of the second group of modes to 187 hZ.

Did you find out yet what dimensions your local suppliers carry in lumber? If they're different, we'll have to re-calculate a few things. At least, you sound like you're getting a good understanding of the basic design ideas, so re-calculation would only change some dimensions, not the actual design... Steve
 

jeeper

Guest
Nightmusic
Frame of a US style house is shown on the page I have linked below. The basics of houses are the same but their are regional variations due to climate and custom differences in different regions. Down south where I am basements are unheard of in the norther colder areas they are under almost every home.
[="http://howstuffworks.lycoszone.com/house6.htm"]Frame of Home[/]

I sure hope this clears up your picture of US wall in case you are still having difficulty.
 

gregmusic

Guest
Hello guys,

Few days have past since my last post,was just in a big working week...
First let me wish all of you a happy new year 2003,with special congratulations to RO which is just one of the best musical site on the Net,truely!Thanks to those people who give their time and knowledge to RO users like me,they are also the reason of the RO success...

So...let's go back to the subject...
Thank u jeeper for your link it was interesting to know how house are built in US when they're made of wood...You know in France that's rare to see that kind of constructions,most of houses are made with plasterboards,or they're brick-built /stone-built ,lumbers are used only for roof construction.Curiously,we can also find wood constructions for chalets,at the mountains,you know where it's cold!

So... today i think most of things are clear in my mind about that broadband absorber construction...

" the vertical studs, which are 1.5" x 3.5", get placed between the two horizontals, with the LONGER (3.5") dimension turned so that from the front of the trap, you would see the NARROW edge of the stud."
Thanks for that precision Steve,now i think i figure out the right thing.So that's the right moment to give you the dimensions lumber that i can find here in Paris:

In millimeter,to avoid translations mistakes:
1)60X80 mm
2)60X40 mm
3)63X75 mm
-------------------->Where us lumbers are in mm:38X89 mm...So i don't know which choice is the better in my case.
One more thing:I still have to go and see them because i just had the information on the net from the main store here in Paris which provides these lumbers .Pictures from the net can sometimes be far from reality.Anyway they don't seem to be radiused,so the dimensions should be the actual ones.But i still have to check if the fir they are made of is strong enough to ensure good solidity,well cut,not curved,etc...
Thanks again,Steve,see you
 
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